The effects of the sun are an ongoing concern for many people who spend their days outdoors. Ultraviolet (UV) light is damaging to skin when the skin absorbs the UV rays. UV light cannot be seen by the human eye. Three types of UV light exist: UVA, UVB, and UVC. Typically, the ozone layer only allows UVA light to pass through, but as the ozone conditions deteriorate over time, it is thought that the amount of UVB passing through the ozone is increasing.
Exposure to UV light is increasing worldwide with the destruction of our protective ozone layer. It is estimated that 90% of UV radiation is of the common UVA type, which can pass through window glass. UVA type is thought to cause tanning and wrinkles in skin. UVB type exposure may depend on ozone quality, and is typically highest at midday. UVB type does not penetrate window glass, and is associated with sunburn. UVB type is considered to be more dangerous than the UVA type. UVC type may be mostly absorbed in the ozone, but is of high concern for the future as ozone conditions deteriorate. UV light has been linked to increases of several diseases such as skin cancer, immune suppression, and cataracts. In particular, skin cancer occurrences have been increasing steadily due in part to the effects of increasing UV radiation passing through our atmosphere.
Sun block is always recommended to prevent sunburn, skin cancer, and overall long term damage to the skin. Most sun blocks, after application, dry clear on the skin. Burns occur when sun block is applied too thinly, or possibly missed entirely. Sun block may lose its effectiveness when exposed to water for long periods of time, or it can rub off when people dry themselves with a towel. It is under these circumstances that it becomes unclear what parts of the body are protected by the sun block.